In a backlight unit structure, generally, a rubber frame with a certain width can be relatively arranged at the edge outside a light guide plate. Due to structural space limitation of the rubber frame and the light guide plate, the edge of the light guide plate is close to, for example, a visible region of a display device, so that the backlight unit has edge bright lines at a large viewing angle. Currently, a narrow frame display has become a development tendency. In a narrow frame structure, the edge of the light guide plate is closer to the visible region, so that the problem of the edge bright lines at a large viewing angle is more serious.